1. Field of the Invention
The present invention is in the field of forced-flow electrochemical batteries.
2. Prior Art
Forced-flow electrochemical batteries are already well known in the art and are, at present, the object of numerous research with a view to equipping non-polluting vehicles.
Among these batteries, air-zinc systems offer considerable advantages for such applications.
An elementary cell of such a battery comprises a catalytic part or positive electrode, on which oxygen from the air is reduced, and an alkaline solution containing zinc powder in suspension, conveyed by means of pumps, which flow over a negative electrode. The oxidation of the zinc and the reduction of the oxygen generate an electric current.
To constitute a battery, it is clearly necessary to couple such elementary cells together both electrically and hydraulically.
Though it is possible to consider feeding the solution to the cells in parallel, it is however observed that if the cells are electrically coupled together in series, leakage currents occur, which are not only detrimental to the electrochemical efficiency, but may also cause gas generation by electrolytic decomposition of the solution, metal deposits, or corrosion.
These leakage currents exist because of electrical potential gradients between individual cells. To substantially reduce the gradient, it is therefore necessary to feed the alkaline solution in series to the cells, in the case where the same cells required to be connected electrically in series.
In this way, sets of cells, hereafter called modules, each comprising a limited number of cells are produced and it is, of course, possible to couple such modulus together with a view to forming a battery having predetermined electrical characteristics and ratings.
Such a coupling method may, in certain cases, have substantial disadvantages, as will be clearly explained in the descriptive part of the present invention.